The present inventive concept herein relates to a semiconductor memory device.
As semiconductor devices are highly integrated, semiconductor memory devices may be required to be miniaturized and have high data storage capacity. Further, semiconductor memory devices may be required to have high operation speed and to be driven at low power. To this end, various types of research are being carried out.
A typical semiconductor memory device may include a number of memory cells that are connected to each other to constitute circuits. A dynamic random access memory (DRAM), which is a representative semiconductor memory device, has a unit memory cell that includes a transistor and a capacitor. Such a DRAM may have a high degree of integration and high operation speed. However, after power is cut off, all data stored in the DRAM is lost.
A flash memory is a representative example of nonvolatile memory devices capable of retaining data even after power is cut off Although the flash memory is nonvolatile, the flash memory may not be highly integrated and may have low operation speed as compared with DRAMs.
For theses reasons, much research have been conducted for developing and improving other nonvolatile memory devices such as magnetic random access memories (MRAMs), ferroelectric random access memories (FRAMs), and phase-change random access memories (PRAMs).